Because all tribes started out nomadic historically I think that legacy should have a nomadic policy.
Here is how I propose it. You can make you tribe nomadic with a nomadic policy. While nomadic you discover new tiles but you people are less happy and can't work with nearly as much efficiency and you can't unlock sedentism or build buildings. This improves many things in the games like making it possible to survive in deserts (ice or otherwise), and that you can find new tiles without having to wait a long times for scouts but it still makes scouts useful, and you have more uses for the now nearly useless authority.
I love legacy and would love to see it grow to it's full potential. I would be honored if my suggestion was used.